In recent years, an individual identification technique using radio waves such as electromagnetic waves for wireless communication has attracted attention. In particular, as a semiconductor device which communicates data by wireless communication, an individual identification technique using an RFID (Radio Frequency Identification) tag has attracted attention. The RFID tag (hereinafter referred to simply as an RFID) is also called an IC (Integrated Circuit) tag, an IC chip, an RF tag, a wireless tag, or an electronic tag. The individual identification technique using an RFID has been useful for production, management, and the like of an individual object, and has been expected to be applied to personal authentication.
Depending on whether a power supply is incorporated in an RFID or whether a power supply is supplied from outside, the RFID can be divided into two types: an active type RFID capable of transmitting radio waves including information on the RFID, and a passive type RFID which is driven using radio waves from outside or power of radio waves (carrier waves) (the active type RFID is referred to Reference 1: Japanese Published Patent Application No. 2005-316724; and the passive type RFID is referred to Reference 2: Japanese Translation of PCT International Application No. 2006-503376). Of these, the active type RFID has a structure in which a power supply for driving the RFID is incorporated and a cell is provided as the power supply. In addition, the passive type RFID has a structure in which a power supply for driving the RFID is generated using power of radio waves (carrier waves) from outside, so that a structure without a cell is realized.
FIG. 31 is a block diagram showing a specific structure of an active type RFID. In an active type RFID 3100 of FIG. 31, a communication signal received by an antenna circuit 3101 is inputted to a demodulation circuit 3105 and an amplifier 3106 in a signal processing circuit 3102. The communication signal is usually transmitted after a carrier such as a 13.56 MHz carrier or a 915 MHz carrier is processed using ASK modulation, PSK modulation, or the like. Here, in FIG. 31, an example of a 13.56 MHz carrier is shown as the communication signal. In FIG. 31, a clock signal which is a reference for processing a signal is required, and a 13.56 MHz carrier is used as a clock here. The amplifier 3106 amplifies the 13.56 MHz carrier and supplies it to a logic circuit 3107 as the clock. In addition, the ASK modulated communication signal or the PSK modulated communication signal is demodulated by the demodulation circuit 3105. The signal which has been demodulated is also transmitted to the logic circuit 3107 to be analyzed. The signal analyzed by the logic circuit 3107 is transmitted to a memory control circuit 3108, and based on it, the memory control circuit 3108 controls a memory circuit 3109, and data stored in the memory circuit 3109 is taken out and transmitted to a logic circuit 3110. The signal stored in the memory circuit 3109 is subjected to encode processing by the logic circuit 3110 and then amplified by an amplifier 3111, so that the carrier is modulated by a modulation circuit 3112 with the signal. Here, a power supply in FIG. 31 is supplied by a cell 3103 provided outside the signal processing circuit through a power supply circuit 3104. The power supply circuit 3104 supplies power to the amplifier 3106, the demodulation circuit 3105, the logic circuit 3107, the memory control circuit 3108, the memory circuit 3109, the logic circuit 3110, the amplifier 3111, the modulation circuit 3112, and the like. In this manner, the active type RFID operates.
FIG. 32 is a block diagram showing a specific structure of a passive type RFID. In a passive type RFID 3200 of FIG. 32, a communication signal received by an antenna circuit 3201 is inputted to a demodulation circuit 3205 and an amplifier 3206 in a signal processing circuit 3202. A communication signal is usually transmitted after a carrier such as a 13.56 MHz carrier or a 915 MHz carrier is processed using ASK modulation, PSK modulation, or the like. Here, in FIG. 32, an example of a 13.56 MHz carrier is shown as a communication signal. In FIG. 32, a clock signal which is a reference for processing a signal is required, and a 13.56 MHz carrier is used as the clock here. The amplifier 3206 amplifies the 13.56 MHz carrier and supplies it to a logic circuit 3207 as the clock. In addition, the ASK modulated communication signal or the PSK modulated communication signal is demodulated by the demodulation circuit 3205. The signal which has been demodulated is also transmitted to the logic circuit 3207 to be analyzed. The signal analyzed by the logic circuit 3207 is transmitted to a memory control circuit 3208, and based on it, the memory control circuit 3208 controls a memory circuit 3209, and data stored in the memory circuit 3209 is taken out and transmitted to a logic circuit 3210. The signal stored in the memory circuit 3209 is subjected to encode processing by the logic circuit 3210 and then amplified by an amplifier 3211, so that the carrier is modulated by a modulation circuit 3212 with the signal. On the other hand, the communication signal inputted to a rectifier circuit 3203 is rectified and is inputted to a power supply circuit 3204. The power supply circuit 3204 supplies power to the amplifier 3206, the demodulation circuit 3205, the logic circuit 3207, the memory control circuit 3208, the memory circuit 3209, the logic circuit 3210, the amplifier 3211, the modulation circuit 3212, and the like. In this manner, the passive type RFID operates.